Hi,
NAS refers to the NAV Application Service. This is a service that runs and within NAV you can setup a job queue. WIthin the job queue you will define what needs to run and when. So you can handle the setup within NAV and the NAS will handle the processing of it. Be aware that the NAS is a service and therefore cannot handle windows. So therefore you need to make sure that the code is not opening any windows (like processing bars or confirmation popups).
Information about job queue for NAV 2013 R2 (but this feature has been available in previous versions):
msdn.microsoft.com/.../hh879427(v=nav.71).aspx
Hope this is helpful. You can find a lot of information on MSDN or of course google, on how to setup a NAS and use the job queue (msdn.microsoft.com/.../aa496089.aspx).